DE2313849A1 - FLOW PRESSURE MEASURING CIRCUIT - Google Patents

Description

Fluid pressure measuring circuit

The invention relates to measuring devices, in particular those 'devices which a fluid for measuring dimensional changes in workpieces use.

Back pressure gauges have long been known in the art and usually consist of a tool that is connected to a an air nozzle fed under controlled pressure fluid. Pressure changes upstream of the nozzle by changing the distance between the workpiece and the display head, are used to measure these sections and thus the dimensional changes in the workpiece.

While this arrangement is generally satisfactory, it inherently has at least two important limitations:

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1. Extremely restricted area. The interaction between the nozzle and the workpiece necessary to produce the interacting changes in back pressure occurs only over one:; extremely restricted area. For example, one! Nozzle diameter of 2 mm a linear range of only 0.2 mm; obtain. This limits the usefulness of an existing ■

j teaching in some cases and also creates difficulties in

ι Test setup as well as other disadvantages. ί

2. The beam force exerted on the workpiece changes with the distance between the workpiece and the jig tool. While this effect may be insignificant if the circle is at Rigid workpieces and is used with a rigid attachment, these changes in the measuring force can be great when measuring of flexible workpieces generate significant defects.

To overcome these disadvantages, the present invention provides a fluid gauge of the type mentioned above, in which the pressure immediately upstream of the jig tool either by manual adjustment or by a feedback servo line loop is held constant and at which the extent of this adjustment necessary to keep the pressure constant is measured is used to display the changes in distance to be measured. In which In the preferred embodiment, the measurement is carried out by providing an upstream flow restriction.

309840/0

The resulting change in pressure above the fixed
The restriction upstream of the measuring tool is used to measure these changes in distance with respect to the workpiece. j

The invention will now be explained by means of examples with reference to! the drawing described. FIGS. 1 and 2 show two embodiments examples of the invention. ,

In the drawing, in particular in FIG. 1, a counter pressure circuit;

10 shown schematically.

This circle shows a constant pressure, such as air pressure, standing fluid source 12 on. The fluid is cleaned as it flows through a conventional air filter 14 before it is directed to a regulator 16 which has manual means 18 for adjusting the pressure upstream thereof.

The pressurized fluid is passed through a channel 20 and a throttle point 22 to the measuring tool 24, which is with
openings 26 and 28 is provided. Both openings can do one
Direct the fluid jet at the workpiece 30.

The throttle 22 is adjusted so that it creates a given pressure drop across it, so that the pressure is upstream
always deviates from the pressure prevailing downstream,
as long as fluid emerges from the openings 26 and 28.

3D984Q / 038S

A manometer 32 can indicate the pressure downstream of the restriction, while a manometer 34 is provided which is responsive to the “ pressure upstream thereof.

i ■ ι

ι In operation, an operator controls each reading ler 16 so that the pressure downstream of the throttle point 22 I (indicated by the manometer 32), remains constant. This one j

position in turn causes a pressure change upstream of the throttle point 22. This change in turn is related to Distance between the measuring tool 24 and the workpiece 30, since this distance is the one indicated by the manometer 32 to be kept constant Pressure controls.

For this purpose, the pressure gauge 34 can be read directly be calibrated in millimeters or another unit of measurement.

It is to be emphasized that the radiation force on the workpiece does this tends to be kept at a constant level, since the pressure at the openings 26 and 28 is increased when the measured workpiece surface away from the measuring tool 24 in order to compensate for the reduced throttling effect on the fluid nozzles.

It has been found that in a similar manner for the same reason the range of such distances in which the required Interrelationship between the market piece development and that resulting from it generated back pressure remains designated, is increased.

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To the need for manual adjustments at each reading To be eliminated, a feedback line loop can be provided as shown schematically in FIG. 2.

In this embodiment, all elements are the same as in Fig. 1. However, the pressure becomes downstream of the throttle point passed through a channel 36 to a servomechanism 38, which can operate the controller 16 so that a con at this point constant pressure is maintained.

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Claims (3)

Patent attorneys Dr. ing. H. Nfegendank Dfpl. Ing.H. Haucfc - Dioi. Pirys. W. Schmitz DIpI. Ing. E. Graalfs - Dip ». Ing. W. Wehnert 8 Munich 2, MozaristraSe 25 Telephone 538058ε The Bendix Corporation Executive Offices Bendix Center March 19, 19 73 Southfield.Mich.48075, USA Attorney's file M-2571 patent claims 1./Smuungsmitteldruckmeßkreis for measuring a workpiece, be standing out of a measuring tool with at least one on one. Surface of the workpiece directed opening and a device for supplying pressurized fluid to the measuring tool, said device comprising a channel with a connected upstream of the measuring tool throttle point, characterized by a device for adjusting of the pressure upstream of the throttle point (22) in such a way that the pressure downstream of the throttle point is at a constant Value is held, and by means for displaying the corresponding changes in distance from the measuring tool (24) to the workpiece surface (30) as a function of these settings. 2. Measuring circuit according to claim 1, characterized in that the display device has a device that operates on the medium pressure responds upstream of the throttle point (22), ί 3. Measuring circuit according to claim 2, characterized in that the one! direction for adjusting the fluid pressure upstream '■ Windwärts the throttle point (22) a manually operated Strömungsmit- | i is the pressure regulator (16). 4. Measuring circuit according to claim 2, characterized in that the device for adjusting the fluid pressure upstream of the throttle point (22) is a pressure regulator operated by a servomechanism (18) is actuated, which via a feedback line loop on the fluid pressure downstream of the Throttle point responds. 5. A method for measuring a workpiece by means of flow center pressure, characterized in that pressurized fluid is directed through an opening onto a surface of the workpiece to be measured that the pressure at the opening is kept constant during the distance changes between the display head and the workpiece by adjusting the Pressure upstream of the opening head, and that the The required adjustment level is measured to keep this pressure constant is thereby assigned to one of the distance changes Measurement to get. 3Q9S4Ü / Q388 _...... 6. The method according to claim 5 _9, characterized in that the measurement of the adjustment is achieved by measuring the pressure upstream of a throttle point arranged upstream of the opening. 3 Q 9 8.4 0/03 8 8